Wireless communication systems are known to include a central controller, a plurality of communication units, communication resources, and repeaters that transceive the communication resources. In such communication systems, communication units are generally grouped by like function or usage. For example, communication units operated by a police department may be grouped together. This group may be further divided into subgroups based on police districts. While another group of communication units may be operated by a fire department which may also be divided into subgroups.
Typically, in communication systems, the groups do not communicate with each other. This is the case when one group of communication units is operated by a trucking company and another group of communication units is operated by a taxi cab company. In such a system, which is referred to as a shared communication system, one group will not communicate with the other groups, nor are they aware of the other groups. By having a variety of groups independently operating on a system, the system is operated closer to its maximum capacity, thus reducing the cost for the user. But, under heavy use of the system, some requests for communication will be delayed, which is a trade off for the reduced cost.
If the user cannot afford the delay in processing communication requests or requires the groups to communicate with each other, at least once in a while, the user will want a private system. For example, a municipality generally purchases a private system for their public safety organizations, where the public safety organizations may be a police department, fire department, city government, public works, parks and recreation, and sanitation. Each of these public safety organizations would be a separate communication group, i.e., a group that normally communicates with it members only. But, when a particular emergency occurs within the municipality, such as a fire, the police department and the police department may need to communicate with each other to effectively respond to the fire.
When the user first purchases its private system, or when the private system is reinitialized after a system shutdown, all entries in a communication unit identification code (ID) database are default enabled. The communication unit ID database contains up to 64,000 entries of valid unit IDs. As is known, a valid unit ID must be transmitted by a communication unit with any system service request. Thus, any unit with one of these 64,000 IDs can access the private system.
As is also known, a purchaser of a private system typically purchases less than a few thousand communication units. Thus, only a few thousand of the 64,000 IDs are needed. To allow only the communication units purchased to access the private system, a system manager must "activate" the unit IDs of the purchased communication units and "deactivate" the other unit IDs in the communication unit ID database. This is a relatively simple process where the system manager "activates" the appropriate unit IDs by setting an "active flag" within the communication unit ID database. To "deactivate" a unit ID, the system manager simply sets a "not default enabled flag" for the particular ID. If neither flag is set, as in the case when the system is initialized or reinitialized after a shutdown, all unit IDs are default enabled. Thus, default enabled IDs and activated IDs are valid, i.e., allows a communication unit using one of these IDs to access the private system, and deactivated IDs are invalid, i.e., communication units using one of these IDs will not be allowed access to the private system.
At a cursory view, it would seem to make more sense to deactivate all the IDs at initialization or upon a reinitialization. Thus, guaranteeing that only communication units having activated IDs would be allowed to access the private system. But, upon a closer examination, most private systems are operated by public safety organizations that do not have time to wait for a system manager to activate a few thousand communication unit IDs before they respond to an emergency condition. Thus, the private systems are designed to operate with the default enabled IDs, until the system manager activates and deactivates the unit IDs.
Unfortunately for the purchaser of the private system, if the system manager does not deactivate all of the unused unit IDs, a communication system "hacker" may allow unauthorized communication units, i.e., communication units that were not purchased by the operator of the private system, to access the private system via the unused default enabled IDs. When a hacker uses the unused default IDs, the private system is no longer private, in that, the purchaser of the private system is sharing its system with unauthorized users. Thus, the premium the user paid to have a private system has been wasted.
Therefore, a need exists for a method that prevents unauthorized users to access a communications system.